package ch3.section3.myArrayList;

/**
 * ArrayList的实现
 * @param <AnyType>
 */
public class MyArrayList<AnyType> implements Iterable<AnyType> {
    private static final int DEFAULT_CAPACITY = 10;

    private int theSize;
    private AnyType[] theItems;

    public MyArrayList(){
        doClear();
    }

    public void clear(){
        doClear();
    }

    private void doClear(){
        theSize = 0;
        ensureCapacity(DEFAULT_CAPACITY);
    }

    public int size(){
        return theSize;
    }

    public boolean isEmpty(){
        return size() == 0;
    }

    public void trimToSize(){
        ensureCapacity(size());
    }

    public AnyType get(int idx){
        if(idx < 0 || idx >= size()){
            throw new ArrayIndexOutOfBoundsException();
        }
        return theItems[idx];
    }

    public AnyType set(int idx,AnyType newVal){
        if(idx < 0 || idx >= size()){
            throw new ArrayIndexOutOfBoundsException();
        }
        AnyType old = theItems[idx];
        theItems[idx] = newVal;
        return old;
    }

    public void ensureCapacity(int newCapacity){
        if(newCapacity < theSize){
            return;
        }
        AnyType[] old = theItems;
        theItems = (AnyType[]) new Object[newCapacity];
        for(int i = 0;i < size();i ++){
            theItems[i] = old[i];
        }
    }

    public boolean add(AnyType x){
        add(size(),x);
        return true;
    }

    public void add(int idx, AnyType x){
        if(theItems.length == size()){
            ensureCapacity(size() * 2 + 1);
        }
        for(int i = theSize;i > idx;i --){
            theItems[i] = theItems[i-1];
        }
        theItems[idx] = x;
        theSize ++ ;
    }

    public AnyType remove(int idx){
        AnyType removedItem = theItems[idx];
        for(int i = idx;i < size() - 1; i++){
            theItems[i] = theItems[i+1];
        }
        theSize --;
        return removedItem;
    }

    @Override
    public java.util.Iterator<AnyType> iterator(){
        return new ArrayListIterator();
    }

    private class ArrayListIterator implements java.util.Iterator<AnyType>{

        private int current = 0;

        @Override
        public boolean hasNext() {
            return current < size();
        }


        @Override
        public AnyType next() {
            if(!hasNext()){
                throw new java.util.NoSuchElementException();
            }
            return theItems[current++];
        }

        @Override
        public void remove() {
            MyArrayList.this.remove(--current);
        }
    }

}
